https://hdl.handle.net/20.500.12809/52 2026-04-04T08:07:50Z 2026-04-04T08:07:50Z Diler, Harun Kasal, Ali Kuşkun, Tolga Erdil, Yusuf Ziya Güray, Ersan https://hdl.handle.net/20.500.12809/11039 2023-10-25T11:42:48Z 2023-01-01T00:00:00Z

Strength Classification of Wooden Chairs under Cyclic Loads Based on an Experimental Study Diler, Harun; Kasal, Ali; Kuşkun, Tolga; Erdil, Yusuf Ziya; Güray, Ersan This study aimed to assess the cyclic load capacity of wooden chairs and subsequently categorize them based on their performance. A diverse selection of chair models was randomly procured from commercial markets. These chairs underwent performance testing, utilizing the cyclic stepped increasing loading method, with adherence to the standards set forth by the American Library Association Technology Reports (ALA). The study evaluated 315 chairs, encompassing 21 chair models. Each chair model underwent five replications of testing across three different loading directions. The resulting dataset of numerical values was subjected to statistical analyses, facilitating the categorization of chairs based on their strength under cyclic loads. Notably, the study revealed substantial variations in the load capacity among different chair models. As a consequence of this investigation, the study established acceptable design load thresholds. For instance, concerning front-to-back loading, it was determined that the chairs with cyclic load capacities ranging from 932 to 1449 N fell within the category of low-strength, between 1450 and 1968 N were classified as medium-strength (suitable for domestic use), and the chairs with cyclic load capacities exceeding 1968 N were considered to possess high strength (intended for hotel lobbies, restaurants, libraries, etc.). Similarly, for back-to-front loading performance, the study identified the chairs with cyclic load capacities between 625 and 895 N as low-strength, 896 and 1167 N as medium-strength, and the chairs with loads surpassing 1168 N as high-strength. The performance thresholds for side thrust loads were as follows: low-strength encompassed the cyclic load capacities ranging from 649 to 934 N, medium-strength spanned the cyclic load capacities between 935 and 1221 N, and high-strength entailed 1222 N and above. Notably, the classification devised in this study is closely aligned with the widely accepted and internationally recognized ALA specification. This strong consistency with global standards reinforces the reliability and applicability of the classification system developed in this research. In conclusion, this study enhances understanding of wooden chair strength performance and offers practical insights that lead to higher-quality products and improved consumer satisfaction. Its recommendations can potentially drive positive change within the industry and benefit manufacturers and consumers.

2023-01-01T00:00:00Z Utkucan Şahin Yan,Chen https://hdl.handle.net/20.500.12809/11036 2023-10-25T07:55:09Z 2023-01-01T00:00:00Z

Assessing the current and future effects of Covid-19 on energy related-CO2 emissions in the United States using seasonal fractional grey model Utkucan Şahin; Yan,Chen Accurate CO2 forecasting plays an important role in energy planning. However, in the annual forecasting studies on CO2 emissions, the seasonal effects cannot be predicted. To overcome this problem, this study proposed a novel prediction model based on the seasonally optimised fractional nonlinear grey Bernoulli model (SOFANGBM(1,1)), combining the seasonal fluctuation technique with optimisation of the background, power index, and fractional order values. The proposed novel model offers two important improvements in prediction performance: (1) This model combined optimised fractional nonlinear grey Bernoulli model (OFANGBM(1,1)) with the seasonal fluctuation technique to enable monthly and quarterly predictions (2) The seasonally optimised fractional nonlinear grey Bernoulli model (SFANGBM(1,1)) was improved by optimising the background value. CO2 emissions had the largest share in global GHG emissions, and the United States was the second largest CO2 emission emitter worldwide after China in 2019. However, cases and deaths from Covid-19 continue in the United States, and important questions arise: How has Covid-19 affected CO2 emissions by fossil fuel type in the past, and how will it reshape them in the future? This study aimed to analyse how Covid-19 affects CO2 emissions from fossil fuels in the U.S., how it will reshape its future, and also contribute to Sustainable Development Goals (SDGs). Quarterly CO2 emissions from coal, natural gas, petroleum, and total CO2 emissions in the U.S. were forecasted using a novel grey prediction model under pandemic and pandemic-free scenarios. The pandemic-free scenario determined the CO2 emissions gap due to Covid-19, and the pandemic scenario presented forecasted results of quarterly and annual CO2 emissions by 2025. The prediction performance was tested from 2022-Q1 to 2022-Q4 by simulated from 2015-Q1 to 2021-Q4. Using the SOFANGBM(1,1), Covid-19 caused 2 %, 2 %, 16 %, and 12 % reductions in CO2 emissions from coal, natural gas, petroleum, and total CO2 emissions, respectively, in 2020. SOFANGBM(1,1) also forecasts that total CO2 emissions will reach 4520.6 Mt by 2025.

2023-01-01T00:00:00Z Güler, Onur Vahip Gürel, Barış Aryanfar, Yashar Castellanos, Humberto Garcia Göltaş, Merve Keçebaş, Ali Akkaya, Volkan Ramazan https://hdl.handle.net/20.500.12809/11034 2023-10-25T06:41:10Z 2024-01-01T00:00:00Z

Thermo-hydraulic efficiency of lung-inspired compact plate heat exchangers made using additive manufacturing techniques with steel, aluminum and titanium powders Güler, Onur Vahip; Gürel, Barış; Aryanfar, Yashar; Castellanos, Humberto Garcia; Göltaş, Merve; Keçebaş, Ali; Akkaya, Volkan Ramazan The selection of material for compact plate heat exchangers (CPHEs) is of increasing importance due to global economic and supply constraints. Additionally, the influence of material selection on the thermo-hydraulic characteristics of CPHEs is an area of ongoing research. This study aims to address these issues by analyzing the thermo-hydraulic performance of CPHEs made from steel, aluminum, and titanium materials with small, complex channels. Using an additive manufacturing method (specifically Direct Metal Laser Sintering), lung-inspired CPHEs of identical geometry and roughness were manufactured from steel, aluminum and titanium powders. The thermo-hydraulic characteristics of CPHEs as well as that of a traditional one with Chevron-type, were investigated using both experimental and numerical techniques under specific operating conditions to determine the optimum between maximum heat transfer and minimum pressure drop. The findings of this study reveal that as the temperature difference between the inlet on the hot and cold sides, as well as the flow rate, were increased, there was a corresponding increase in both amount of heat transferred and loss of pressure across all investigated CPHEs. Compared to the chevron type brazed plate heat exchanger, the CPHE made from aluminum showed a 75.2 % and 11.2 % increase in heat transfer and a 31.8 % and 10.9 % reduction in pressure drop at 3 and 6 L/min, respectively, for a temperature difference of 90–40 °C. This study suggests that the use of materials with different thermal conductivities in CPHEs may offer a promising solution to achieve elevated heat transfer rates while minimizing pressure drop.

2024-01-01T00:00:00Z Gülbaş, Gülşah Çetin, Gürcan https://hdl.handle.net/20.500.12809/10983 2023-09-27T10:35:13Z 2023-01-01T00:00:00Z

Lifetime Optimization of the LEACH Protocol in WSNs with Simulated Annealing Algorithm Gülbaş, Gülşah; Çetin, Gürcan The lifetime of a Wireless Sensor Network (WSN) is determined by its energy restriction. One of the conventional techniques used to maintain network connectivity is the utilization of the LEACH routing protocol. LEACH is based on clustering, and the process of choosing a Cluster Head (CH) in each round is based on chance. Consequently, it remains unclear whether the best CH is selected for each round. In this study, two approaches based on the Simulated Annealing (SA) algorithm are described to minimize energy losses of the nodes and improve the lifetime of the WSN utilizing the LEACH routing protocol. In both techniques, the residual energies at the nodes, as well as their distances from each other, are taken into consideration when determining the CHs. The efficiency of the presented approaches has been evaluated for networks with 10, 25, 50 and 100 sensors in terms of consumed energy, total data packets received by the Base Station (BS), the number of active/dead nodes, and the average energy per sensor. According to the findings, the PSCH-SA technique yields the most favorable results in networks with 10 sensors, while the LEACH-SA protocol demonstrates superior performance in WSNs with 25 or more sensors.

2023-01-01T00:00:00Z